The Nurali Massif in the Urals echoes the findings of the Lanzo Massif. Nurali is a peridotite body which is part of an ophiolite complex bounded on the west by the Main Uralian Fault and on the east by gabbros and a serpentinized tectonic mélange. This system of ophiolites was emplaced during the Uralide orogeny and preserves the rifted margin of the Paleo-Uralian Ocean (Puchkov, 2009; Spadea et al., 2003).. Throughout the peridotite, sigmoidal patterns of foliation suggest the presence of anastomosing shear zones. The foliation in the dunite and gabbro units dip steeply (~80º) westward towards where the Paleo-Uralian coastline would have been. REE and LREE analysis suggests fertilization by MORB-like melts. The easternmost domain of the preserved Nurali rifted margin is often cut by continent-dipping (with respect to the paleogeography) faults. A favored interpretation of the Nurali massif ophiolite is of a continent-ocean transition from the opening of the Paleo-Uralian Ocean, where the transition from peridotite to gabbro represents the transition from sub-continental mantle to oceanic crust (Spadea et al., 2003).
One key weakening mechanism implicated at Lanzo and Nurali is dynamic grain recrystallization. Analysis of deformed mineral grains within the anastomosing shear zone at Lanzo shows evidence of chemical disequilibrium and decreasing grain size with degree of deformation, suggesting that high-temperature deformation and melt infiltration were happening simultaneously, with melt-rock interactions and grain recrystallization causing localization of deformation (Higgie & Tomasi, 2014; Kaczmarek & Müntener, 2008; Müntener & Piccardo, 2003). This mechanism is also prevalent at modern slow spreading ridges, such as the SWIR (Bickert et al., 2021) and suggest that it plays an important role in determining the deformation processes in the mantle lithosphere under magma-poor conditions. Recent work by Ruh et al. (2021) showed that lithospheric-scale shear zones, in which diffusion creep is dominant and grain size reaches down 100  reduce lithospheric strength and dominates tectonic deformation. They used a paleowattmeter to calculate grain size (Austin & Evans, 2007). Viscosity was obtained by calculating the geometric average of diffusion and dislocation creep and by using the slow rate of grain growth on the order of millions of years given by (Speciale et al., 2020). Here we approach the same process using the work of Bickert et al. (2020) that provides an additional constraint to the onset of DRX at high temperature in the mantle lithosphere. DRX initiates for a given critical strain for a given temperature and strain rate condition in a wide range of materials (Jonas & Poliak, 2003; Poliak & Jonas, 1996; Sakai et al., 2014). Materials undergoing dynamic grain recrystallization first undergo a phase of hardening until a maximum stress is reached after which strain softening occurs (Cho et al., 2019; Sakai et al., 2014). This phenomenon is observed for DRX in olivine at various strain rates and temperatures (Hansen et al., 2012). In order to simulate the onset of DRX in a mantle lithosphere primarily composed of dry olivine deforming by dislocation creep we chose the approach of Poliak and Jonas (1996) which states that DRX occurs for a critical energy threshold,  corresponding to a critical stress,  for a range of strain rate,    (  is the square root of the second invariant of the strain rate tensor or effective strain rate). This critical condition occurs when the amount of tectonic work provided is equal to the rate of irreversible deformation in the olivine crystal. Here we assume that the critical stress corresponds to an effective stress of 200 MPa estimated from recrystallized grain sizes in shear zone samples from the SWIR (Bickert et al., 2021; Bickert et al., 2020). We chose an effective strain rate of 10-14 s-1 to match long term tectonic evolution rates of deformation. This is a crucial assumption as localization in lithospheric scale mantle shear zone will control the strength and weakening of the mantle lithosphere.
2 Ivorian OCT imaged by reflection seismic data
2.1 Geological context
The Ivorian (or DICB) rifted margin and its Brazilian Para-Maranhao conjugate formed as one of the Equatorial Atlantic pull-apart rift segments formed between separating Africa and South America at Cretaceous times. It formed between the Saint Paul and Romanche transforms located respectively north and South of the present-day DICB (Fig. 3a). Rifting started in the early Barremian (~131 Ma) and lasted until the Late Albian when lithospheric breakup occurred separating the DICB from the Para-Maranhao rift basins with the Equatorial Atlantic oceanic crust (Blarez, E. & Mascle,1988; Basile et al., 1993, 2005; Labails et al., 2010; Moulin et al., 2010; Gillard et al; 2019). From this time onwards, post-rift sedimentation passively sealed the DICB ocean-continent transition imaged by both seismic reflection and field method data we use in this study (magnetic and gravity anomaly from www.geomapapp.org / CC BY, Ryan et al., 2009, Fig. 3b & 3c).
Depth-migrated seismic reflection data of the Ivory Coast reveal a non-overprinted ocean-continent transition in high resolution and in three dimensions. The area of study provides a coverage from the tip of the thinned continental crust to the first tabular oceanic crust from proximal to distal (Fig 3). It is noteworthy that this OCT was reported to be magma-poor by Gillard et al. (2019) who proposed it is formed by a “hybrid” crust made of exhumed mantle rocks overprinted by subsequent magmatic additions. Here we further use a 3D seismic dataset to characterize the spatio-temporal interaction between extensional tectonics and magmatism transitionally leading to steady-state seafloor spreading.